Whitby & District Astronomical Society

In this month's Sky Notes:

• Planetary Skylights
• Meteors
• April 2020 Sky Charts

Planetary Skylights

Evening Planets

Venus rules in the evening sky, whilst Mars, Jupiter and Saturn vie for attention in the dawn sky.

Venus will continue to dominate the pre-midnight evening sky during April, a 

brilliant beacon hard not to miss! At the start of the month Venus is involved in a spectacular conjunction with the lovely star cluster known as the Pleiades or Seven Sisters.

Observe over the first couple of evenings of April as Venus edges ever closer to the cluster, passing through the eastern fringes of the group on April 3rd. The view will be best appreciated through binoculars or a short focal length telescope at low power, which will also reveal the phase of Venus, which changes gradually to a crescent by the end of April.

Bear in mind that Venus is just a few tens of millions miles away, whereas the Pleiades members reside around 410 light years! If you have one, use a screw on colour filter (yellow or green) to reduce the glare from Venus and more comfortably distinguish the phase and perhaps even some subtle darker marking in the cloud duvet.

Venus reaches greatest brilliancy on April 28^th – a brilliant - 4.7 in magnitude, bright enough to cast a shadow. A crescent Moon lies lower left of Venus on the 27^th. 

Jupiter, Mars and Saturn are all located low in the east – southeast dawn sky.  Of these, Jupiter is by far the most conspicuous to the eye, visible from 05:00h until dawn. 

To the left of Jupiter, resides pearly white Saturn, relatively prominent, but only a quarter the brilliance of Jupiter. Mars lies a little further to the east and is the least conspicuous of the three planets. The ‘Red planet’ has a distinct amber hue, but as yet is disappointing when viewed telescopically, the diminutive disk still too distant to reveal detail.

Even though far more distant than Mars, Jupiter and Saturn, the two largest planets in the solar system, have much to scrutinise in the eyepiece. Jupiter exhibits the cloud belts, great red spot and Galilean moons, whilst Saturn’s ring system is still orientated to us. A word of caution, the low altitude of these planets will make observations somewhat reliant on those moments of ‘good seeing’, so patience at the eyepiece is required. The waning Moon passes below Jupiter and Saturn on the 15^th and Mars the following morning. 

15-Apr-2020 at 05:15h (SE): Jupiter, Saturn, Mars and The Moon.  (Click for full-sized image)

 

16-Apr-2020 at 05:15h (SE): Jupiter, Saturn, Mars and The Moon.  (Click for full-sized image)

 

 

Meteors

This month’s most prolific meteor shower; the Lyrids, last from about April 16^th until April 25^th, peaking over the last hour of the 21^st into the early morning hours of the 22^nd this year.

The Lyrids are associated with comet Thatcher (C/186 G1) a periodic comet taking approximately 415 years to orbit the Sun. The comet last visited us in 1861.

Each April Earth plows through debris left behind by the comet giving rise to the shooting stars we observe. Lyrids are typically as bright as a second magnitude star, but as with most meteor showers there is always the chance of witnessing something a great deal brighter. These so called ‘Lyrid fireballs’ can exceed Venus in brilliance (which currently dominates the evening sky). Such shooting stars can momentarily cast a shadow, sometimes leaving behind smoking debris trails that can linger for over a minute.

Remember though that the vast majority of meteors are no bigger in size than instant coffee granules and even the really bright ones only marble sized!

The radiant of the shower lies not far from the lovely brilliant steely blue star Vega in Lyra - the Harp, which during the early morning hours is rising into the north east aspect. Observing at such a time, expect to spot 10-20 meteors per hour on the 22^nd. Do not however look in the direction of Lyra, but instead view at least two hand spans away from it. The Moon is new on the 23^rd – so prospects for the shower are very favourable.

A number of lesser meteor showers occur during April. The Virginids and alpha Scorpiids each have zenith hourly rates (ZHR) of half a dozen, or so, equating to ‘normal’ sporadic meteor activity levels. The Virginids peak over the night of April 7/8th, which coincide with the Full moon and will be drowned out. The Scorpiids peak on the 27th and will fare better but you will have to observe in the early morning hours. 

 

 

April 2020 Sky Charts

Looking North Mid-April - 21:30h	Looking South Mid-April - 21:30h
Looking East Mid-April - 21:30h	Looking West Mid-April - 21:30h
Northern Aspect Mid-April - 21:30h	Southern Aspect Mid-April - 21:30h
Looking North (Early) Mid-April - 04:30h	Looking South (Early) Mid-April - 04:30h

 

Additional Image Credits:

• Planets and Comets where not otherwise mentioned: NASA
• Sky Charts: Stellarium Software

 

 

The start of April offers up an interesting stellar challenge, testing the observing dexterity of astronomers; casual or otherwise in a race against time..  This is all about spotting first magnitude stars; those ranked brightest in the sky.

Piercing the spring twilight dotted around the sky, no less than thirteen of these are currently visible, more than at any other time of year.  However the window of opportunity in which to identify these stellar jewels rapidly diminishes as we head deeper into April, from little over an hour at the start, to just fifteen minutes by mid month.  You will require clear views right around the horizon and complicating matters further, a number of planets may confuse the unwary. 

You will require clear views right around the horizon and complicating matters further, a number of bright planets may confuse the unwary. 

Let us assume it is late March (post clock change i.e BST time) or early April, at which time twilight deepens around 9pm. Our first port of call lies over in the west, where the mighty hunter; Orion, is about to lose his right toe, marked by bright Rigel, (1) below the horizon. . A word of caution before we go any further. Two naked eye planets are to be found low in the west late March/early April - Mars and Mercury. Mars will have a distinct orange hue, Mercury may be harder to spot depending on what date you observe, so if the 'star' you are looking at doesn't seem to fit the constellation, well done, you have also spotted two planets.

Above Rigel, Orion’s three belt stars are aligned parallel to the west horizon, but the next star on our list, the conspicuous orange hue of Betelgeuse (3), is located above them. A hand span to the right of Betelgeuse and slightly closer to the horizon another orange star, Aldebaran (4) chief star in Taurus is visible in the ‘V’ of the Hyades cluster. Low in the WSW the brightest star in the sky – sparkling Sirius (5) should be quite unmistakable.

Having picked out this first clutch of stars, there is no time to waste, so raise your gaze somewhat higher, to pick out the next wave of luminaries.

Starting in the SW again seek out the bright solitary white hue of Procyon (6) in Canis Minor located above Sirius and to the left of Orion. Due west and higher still, Castor (7) and Pollux (8) denote the twins of Gemini, which is descending feet first down toward the horizon. At a similar altitude to Gemini further across in the WNW  shines brilliant Capella (9) in Auriga, the only one of our bright seasonal winter stars not to set, being circumpolar from our latitude. Capella will spend the summer months arcing low above the north horizon and tricking the unwary into thinking it's the north star!

Turn and face due south, where midway up you will encounter bright Regulus (10) in the ‘sickle’ asterism of Leo. Our next two luminaries are located in the east. Due east, brilliant Arcturus (11) in the constellation of Bootes is very noticeable, its soft orange hue contrasting markedly with Sirius, the only star of the baker’s dozen brighter than it. Now for a test within a challenge, see how far into April you can spot both Sirius and Arcturus above the horizon at the same time! We still have three stars to locate, the first of which, Spica (2) chief star in Virgo, is just rising in the SE, so to spot it at the same time as the others a clear unobstructed view is required. Caution again- the very conspicuous 'star' above Spica is the planet Jupiter.

So, having viewed west, south and east, direct your gaze toward the North, where low in the North-East brilliant steely blue Vega (12) resides in the constellation of Lyra. Vega almost rivals Arcturus in apparent magnitude, but unlike the ‘guardian of the bear” it is circumpolar from Whitby’s latitude and to the unwary also masquerades as the north star during the winter months.

Our final star, Deneb (13) is located just above the NNE horizon and appears much less brilliant than Vega but is by far the most distant and massive of the stars visited. It too is circumpolar and along with Vega constitutes two of the three stars forming the ‘summer triangle’.

In less than three months, only Arcturus, Capella, Deneb and Vega will remain of our original stellar baker’s dozen, the rest having set.  So, are you up for a fun observing challenge? Have a go!